Ion-exchange materials

Abstract

An ion-exchange material, for example a polymer electrolyte membrane or gas diffusion electrode comprises a semi-crystalline copolymer comprising: a first unit which includes an ion-exchange site; a second crystalline unit; and a third unit which is amorphous. The third unit is used to disrupt the crystallinity of the copolymer thereby to increase its solubility in solvents. The material described may be used in fuel cells.

1 . A polymer electrolyte membrane or a gas diffusion electrode which include a semi-crystalline copolymer comprising: 
 a first unit which includes an ion-exchange site;    a second crystalline unit; and    a third unit which is amorphous.    
     
     
         2 . A polymer electrolyte membrane which includes a semi-crystalline copolymer comprising: 
 a first unit which includes an ion-exchange site;    a second crystalline unit; and    a third unit which is amorphous.    
     
     
         3 . A membrane or electrode according to  claim 1  or  claim 2 , wherein the level of crystallinity in said copolymer is at least 0.5%.  
     
     
         4 . A membrane or electrode according to any preceding claim, wherein said first unit is a repeat unit which includes aromatic group containing moieties linked by —SO 2 — and/or —CO— and/or -Q- groups, where Q is O or S.  
     
     
         5 . A membrane or electrode according to any preceding claim, wherein said second unit is a repeat unit which includes aromatic group containing moieties linked by —CO— and/or -Q- groups, where Q is O or S.  
     
     
         6 . A membrane or electrode according to any preceding claim, wherein said third unit is a repeat unit which includes aromatic group containing moieties linked by —SO 2 — and/or —CO— and/or -Q- groups, where Q is O or S provided, however, that said third unit suitably includes a means to render it amorphous (hereinafter said “amorphous means”) and/or not crystallisable with polyarylether ketones or polyarylthioether ketones and/or not crystallisable with the second unit described above.  
     
     
         7 . A membrane or electrode according to any preceding claim, wherein said third unit comprises a fourth unit which is of formula -Q-Z-Q- wherein Z represents said aromatic group containing moiety, wherein said fourth unit is not symmetrical about an imaginary line which passes through the two -Q- moieties provided, however, that said fourth unit is not derived from dihydroxybenzophenone substituted by groups Q at the 4- and 4′-positions.  
     
     
         8 . A membrane or electrode according to any preceding claim, wherein said copolymer includes a first unit which is of general formula  
       
         
           
           
               
               
           
         
       
       or of general formula  
       
         
           
           
               
               
           
         
       
       or of general formula  
       
         
           
           
               
               
           
         
       
       or of general formula  
       
         
           
           
               
               
           
         
       
       wherein said first unit is functionalised to provide ion-exchange sites; wherein the phenyl moieties in units IV, IV*, V and V* are independently optionally substituted wherein m,r,s,t,v,w and z independently represent zero or a positive integer, E and E′ independently represent an oxygen or a sulphur atom or a direct link, G represents an oxygen or sulphur atom, a direct link or a —O-Ph-O— moiety where Ph represents a phenyl group and Ar is selected from one of the following moieties (i)* and (i) to (x) which is bonded via one or more of its phenyl moieties to adjacent moieties  
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
     
     
         9 . A membrane or electrode according to any preceding claim, wherein said first unit is sulphonated to provide said ion-exchange site.  
     
     
         10 . A membrane or electrode according to any preceding claim, wherein said first unit includes a multi-phenylene moiety or fused ring aromatic moiety which is functionalised to provide said ion-exchange site.  
     
     
         11 . A membrane or electrode according to any preceding claim, wherein said first unit includes a —O-biphenylene-O— or —O-naphthalene-O— moiety.  
     
     
         12 . A membrane or electrode according to any preceding claim, wherein said second crystalline unit is of general formula IV or IV* as described in  claim 8 , provided said unit is crystalline.  
     
     
         13 . A membrane or electrode according to any preceding claim, wherein said third unit is of general formula IV, IV*, V or V* provided said unit is amorphous.  
     
     
         14 . A membrane or electrode according to any preceding claim, wherein said first unit is selected from -ether-phenyl-ketone-phenyl, -ether-phenyl-ketone-phenyl-ether-phenyl-ketone-phenyl-ketone-phenyl, -ether-biphenyl-ether-phenyl-ketone-phenyl, -ether-phenyl-ether-phenyl-ketone-phenyl, -ether-naphthalene-ether-phenyl-ketone-phenyl, -ether-phenyl-ether-phenyl-ketone-phenyl-ketone-phenyl, -ether-diphenyl-ether-phenyl-sulphone-phenyl, -ether-phenyl-ether-phenyl-sulphone-phenyl and ether-phenyl-sulphone-phenyl.  
     
     
         15 . A membrane or electrode according to any preceding claim, wherein said second unit is selected from ether-phenyl-ketone-phenyl-ketone-phenyl-, ether-phenyl-ether-phenyl-ketone-phenyl-ketone-phenyl-, ether-phenyl-ether-phenyl-ketone-phenyl-, ether-phenyl-ketone-phenyl-, ether-phenyl-ketone-phenyl-ether-phenyl-ketone-phenyl-ketone-phenyl and ether-biphenyl-ether-phenyl-ketone-phenyl-.  
     
     
         16 . A membrane or electrode according to any preceding claim, wherein said third unit is selected from ether-phenyl-sulphone-phenyl, ether-phenyl-ether-phenyl-sulphone-phenyl and a 1,3-dioxy-4-(phenylcarbonyl)phenyl moiety.  
     
     
         17 . A device selected from a fuel cell, electrolyser or gas diffusion electrode, the device incorporating a semi-crystalline copolymer according to any preceding claim.  
     
     
         18 . A method of manufacturing a device selected from a fuel cell, electrolyser or gas diffusion electrode, the method including the step of using a semi-crystalline copolymer to prepare an ion-conducting element of the device.  
     
     
         19 . A process for the preparation of a semi-crystalline copolymer as described in any of  claims 1  to  16 , the process comprising polycondensing a compound of formula  
       X 1 —BM-X 2    XVI  
       with a compound of formula  
       Y 1 —SU—Y 2    XVII  
       and with a compound of formula  
       Y 1 —XT-Y 2    XVIII  
       and with a compound of formula  
       Z 1 -AM-Z 2    XIX  thereby to prepare a copolymer, wherein Y 1  represents a halogen atom or a group -EH (or -E′H if appropriate) and X 1  represents the other one of a halogen atom or group -EH (or -E′H if appropriate), Y 2  represents a halogen atom or a group -E′H and X 2  represents the other one of a halogen atom or a group -E′H (or -EH if appropriate) and Z 1  and Z 2  represent a halogen atom or a group -EH (or E′H if appropriate);    and wherein BM represents part of a base monomer, SU represents part of a moiety which is functionalised or can be functionalised (suitably independently of other moieties in the copolymer) to provide ion-exchange sites, XT represents a part of a crystalline or crystallisable moiety and AM represents part of an amorphous moiety.